Counters to the Reverse Triangle from bottom of sidemount?

Hey guys, I have a technique related question. I did some searching, but I'm not too sure on the nomenclature, and I didn't find anything anyway.

Essentially, I'm in sidemount. I have one arm close to his head, and for the sake of description, one arm near his legs. He clamps the near-leg arm with his legs. Now, he pushes my head into this, trapping my head and arm in betwixt his head, just like a triangle. Except that I'm facing the opposite way than I would be in a normal triangle. I don't know what it's called; I had guessed reverse triangle.

Anyway, my problem comes with dealing with that. It's not like I've ever been tapped by it, or had it put me in a disadvantageous position. It's just really, really annoying. Everyone holds on to it for dear life, not trying to put me back in the guard, escape or sweep. They just clamp it in there, and squeeze n' pray, if you will.

What I was wondering is, aside from stepping over and sitting on their chest (which is what I've done till now, then I just try to crush them until they let go, afterwards I promptly go for a kneebar), are there any specific counters to this? With bigger guys, or guys with obscenely strong legs, my sit n' crush strategy takes too long (i.e., sparring is already over, and I've wasted my precious few minutes of spartime doing nothing).

TL;DR

Are there any specific counters to the reverse triangle other than sitting on their chest, trying to push their legs off with one hand, and waiting it out?

Try circling to northsouth as they go for it while driving your elbow downward past their hip - use the circling motion to pull your arm out. When it's out and the elbow's down, post your hand blocking their hip.

Also, don't have your arm down there - either keep it up by their arm and head threatening subs or on the mat blocking their hip.

Also be wary of the arm that's not trapped in the triangle. Usually, if a person catches you in a triangle from under your sidemount, he can also kimura that free arm, either finishing you or flipping you over.

Don't leave your arm between their legs. Or at least make sure they can't catch your head too. If they do, try going to knee-on-belly or circle towards north-south and squeeze their head with your knees (seriously).

I usually counter by sliding one knee onto the opponents body, then posturing & kneebarring. As far as I know it's tricky to get that triangle unless they really pull your trapped arm through, so the opponent is likely to threaten the free arm with a kimura/reverse armbar/chicken wing sort of combo.

It's usually when I'm trying some form of far leg attack from the sidemount that most of this happens. I'll keep in mind not to put my hand inbetwixt their legs, or letting my arm hover over/around that area.

Also, I'll go ahead and point out it's usually the bigger folk in class doing this to me (The smallest of which is 6'4'' 280). That's more of an excuse, though. Thanks.